\"\"

\

In a rectangle the opposite sides are parallel.

\

So, alternate interior angles are congruent.

\

\"\"                              (Alternate interior angle theorem)

\

\"\"                       (Definition of congruent angles)

\

\"\"                            (Substitute \"\")

\

\"\"                            (Subtract 3x from each side)

\

\"\"                            (Subtract 11 from each side)\"\"\"\"                        (Write the factors)

\

\"\"           (Zero product property)

\

\"\"             (Simplify)\"\"

\

The values of x are 5 or \"\".